Production of colored direct-positive images



United States Patent Int. Cl. 603:! 1/40, 5/24 US. Cl. 96-100 15 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the production of colored direct-positive images in light-sensitive silver halide emulsions containing aromatic 1,2-dihydrazones in soluble, diffusion-resistant form stabilized by an additional content of an aliphatic aromatic hydroxyl derivative.

The process for the production of direct positive colorphotographic images by means of photographic silver halide emulsion layers containing aromatic 1,2-dihydrazones is described in British patent specification 916,657. In this process the aromatic 1,2-dihydrazones remain un- I changed at the unexposed areas of the silver halide emulsion layers during color-forming development with primary aromatic amines of the p-phenylendiamine type, for example 4-aminodiethyl aniline, and are then oxidized to form colored compounds in a bleaching bath by means of alkali metal ferricyanide, while at the exposed areas the dihydrazones react with the oxidation products of the color-forming developer to form colorless or almost colorless compounds which are stable against oxidation by ferricyanide ions. The above process is of limited utility, since many formulations are not sufficiently stable when the photographic material is stored under the simultaneous influence of heat and moisture. This results in a decrease in the maximum color densities and in a corresponding flattening of the characteristic curve during color-forming development.

In the most unfavourable instances the above undesired effects even occur upon drying the photographic layer during their production.

The object of the present invention is to provide photographic elements which contain the above 1,2-dihydrazones, but which are stable against the effects of heat and moisture.

It has now been found that compounds of the following formula R-NHOH are particularly suitable for stabilizing the foregoing formulations. In this formula, R represents (a) A linear or branched alkyl radical with up to 20 carbon atoms which may be substituted as desired, but preferably with phenyl, e.g. in a benzylor phenylethyl grouping, carboxy or sulfo,

(b) An aromatic ring grouping, preferably aryl rings, in particular naphthyl or phenyl; these groups may in turn be substituted as desired, for example, with halogen, preferably chlorine or bromine, alkoxy groups with up to 18 carbon atoms, hydroxy, carboxy, esterified carboxy whereby the ester grouping is preferably derived from an aliphatic alcohol with up to 20 carbon atoms, sulfo, amino which may be substituted, for example, with acyl radicals, in particular those derived from aliphatic carboxylic acids 3,471,295 Patented Oct. 7, 1969 with up to 20 carbon atoms or from phenyl sulfonic acids, or with alkyl radicals of up to 2-0 carbon atoms, sulfamyl groupings, in which case the amide radical may be substituted as indicated above in respect of the amino groups, or with phenyl radicals or alkyl radicals with up to 20 carbon atoms.

a Preferred are phenyl-hydroxylamine derivatives particularly those containing water-solubilizing groups such as SO H or COOH and long-chain alkyl radicals with 7 to 20 carbon atoms. These substituents may be linked to the phenyl ring either directly or via any intermediate members, for example, a phenyl sulfonamide grouping.

The aromatic 1,2-dihydrazones described in British patent specification No. 916,657 are stabilized by the above hydroxylamines against the simultaneous effect of heat and moisture. This effect is unexpected inasmuch as the simple hydroxylamine or its salts do not produce any improvement in stability. In addition, other additives with a comparable reducing action such as aromatic hydrazines, hydroxamic acids, ascorbic acid and pyrocatechol, are practically ineffective.

The following compounds exhibit particular utility:

I (llnHm /N\ 0- NHOH H 03s C sHa'I III s 03H @NH-S OrQ-NH o H N H-C1BH31 1v HOOCCHz(|JH-NHOH v HOOC-CHr-(EH-NHOH NHOH -o 0 on V1 The hydroxylamine derivatives are preferably added to the emulsions in amounts from 15% to 60% by weight, based on the aromatic 1,2-dihydrazone; that is about 10 to 750 mg. per square meter of the layer. They do not deleteriously affect the silver halide emulsion. According to British patent specification 916,657 or US. Patent 3,186,840 the aromatic dihydrazones are added in amounts of 1-20 g. per liter of silver halide emulsion; that is about 4.5 to g. per mol silver halide. The aromatic dihydrazones suitable for the photographic materials of the present invention are described in the above patent specification and patent as well as in British patent specification 916,658 and US. Patent 3,162,643.

The hydroxylamines may be prepared by methods described in the literature, starting from the corresponding nitro compounds. In cases where the water solubility is reduced, for example by fairly long alkyl radicals, it is EXAMPLE 1 Preparation of the hydroxylamine derivative:

100 g. of 1-octadecyl-2(m-nitrophenyl)-benzimidazole- -sulfonic acid were dissolved in 500 ml. of pyridine. 130 ml. of S-N-hydrochloric acid were added to the solution and 25 g. of zinc powder were introduced with stirring at 25 to 30 C. over a period of 30 minutes. After stirring for another 15 minutes, the reaction mixture wa suctionfiltered. Ice was added to the filtrate and the reaction product was precipitated with hydrochloric acid, suctionfiltered, washed repeatedly with water and, finally, stirred with acetone and sucked dry.

Yield: 74 g. of 1-octadecyl-2-(m-hydroxyaminophenyl)-benzimidazole-S-sulfonic acid.

Photographic application:

To a gelatino-silver iodobromide emulsion of average sensitivity containing about 5 mol percent of silver iodide were added 40 ml. of a 7.5% aqueous solution of saponine, ml. of a 5% methanolic solution of tris-acroleylperhydrotriazine and 25 ml. of a 1% aqueous solution of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene and an aqueous solution of a dihydrazone of the following formula, so that the final layer contained 55 g. of that compound per mol silver halide.

The above emulsion was applied onto a transparent support of celluloseacetobutyrate. The dried layer contained 0.55 g. of Ag per m. and had a thickness of 3 (Material A A comparison material B differed from material A in that 19 g. of 2-m(m-hydroxylaminophenyl)-l-octadecylbenzimidazole-S-sulfonic acid per mol of silver halide were added in the form of a 5% by weight solution in 0.1 N NaOH, and the pH then adjusted to 7.0 with citric acid.

Samples of materials A and B were stored for 7 days at 40 C. and 85% relative humidity. The samples of A and B stored in this way, together with samples of A and B stored cold at +3 C. for the same period, were exposed behind a step wedge and developed for 8 minutes in a color-forming developer of the following composition:

Grams Sodium hexametaphosphate 2.0 p-Diethylaminoaniline sulfate 2.75 Sodium sulfite (anhydrous) 2.0 Potassium bromide 1.5 Potassium carbonate 75.0

Water, 1 liter.

The developed materials were washed, bleached in a potassium ferricyanide bleaching bath and then fixed and washed according to common practice. Sensitometric analysis of the following maximum color densities:

Material A; Material B1 Cold-stored 1. 0 1. 02 After storage at 40 0 0. 30 1. 04

The stabilizing effect of the hydroxylamine derivative is readily apparent.

EXAMPLE 2 Two photographic materials (samples A and B were prepared as described in Example 1. Material B contained an equimolar quantity of compound II, instead of the hydroxylamine derivative referred to in Example 1. After storage, exposure and color-forming development as in Example 1, the following maximum color densities were otbained Material A; Material B 3 Cold-stored 1. 0 1. 01

After storage at 40 C 0.32 1.03

EXAMPLE 3 EXAMPLE 4 Layers containing the direct positive dihydrazone color component stabilized with an organic hydroxyl amine derivative according to the invention can also be used in multi-layer color photographic materials to correct the undesirable absorption of subtractive color couplers, in particular the undesirable absorption of magenta color couplers.

Such a multilayer material can be composed as follows: on a transparent support, for example, of cellulose acetate or polyethylene glycol terephthalate having a subbing layer coated thereon are applied the following layers:

(a) A red-sensitive silver bromide gelatin emulsion which contains 6 mol percent of silver iodide and which further contains per liter emulsion 30 ml. of a 1% aqueous solution of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene, 40 ml. of a 0.1% methanolic solution of the red-sensitizer of the following formula:

250 ml. of a 6% aqueous solution of the sodium salt of the cyanine coupler of the following formula:

CO-NH I 15E121 CH3 40 m1. of a 7.5% aqueous solution of saponin and 9 ml. of a 5% methanolic solution of tris(acryloyl)-perhydrotriazine. The dried layer contains 0.85 g. of silver in the form of silver halide per square meter.

(b) One of the emulsions described in Examples 1-3 sensitized to the green region of the spectrum by adding per liter of emulsion 50 ml. of 1% methanolic solution of the following sensitizing dye:

G=CHC CzHa (c) An intermediate layer of gelatin,

SOaH

40 ml. of a 7% aqueous solution of saponine and 12 ml. of a 5% methanolic solution of tris(acryloyl)perhydrotriazine. The dried layer contains 0.75 g. silver in the form of silver halide per square meter,

(e) A.yellow filter layer consisting of colloidal distributed silver dispersed in gelatin,

(f) A blue-sensitive silver iodobromide gelatin emulsion layer the silver halide of which contains 6 mol percent of silver iodide. The emulsion further contains per liter of casting solution 30 ml. of a 1% aqueous solution of 4-hydroxy-6-methyl-1,3,3a-7-tetraazaindene, 200 ml. of a 10% aqueous solution of the sodium salt of the yellow color coupler CODE COOH

ml. of a 5% methanolic solution of tris-(acroloyl)- perhydrotriazine and 50 ml. of a 7.5% aqueous solution of saponine.

The dried layer contains per square meter 1.43 g. silver in the form of silver halide,

(g) A protecting layer of hardened gelatin.

The above material is exposed to a color original and processed according to common practice by developing and bleach-fixing the exposed material. A colored image of the original in true colors is obtained. An image of the same quality is obtained after storing the above material for several days at 40 C. and high humidity.

What is claimed is:

1. In a photographic light-sensitive silver halide emulsion containing an aromatic 1,2-hydrazone of an alpha dicarbonyl compound and forming a direct positive dye image upon exposure, color development and silver bleaching, the improvement according to which the emulsion also contains an alkyl or aryl hydroxylamine in an amount that stabilizes the unprocessed emulsion against the loss of final color intensity resulting from storage at elevated temperatures.

2. The combination of claim 1 in which the hydroxylamine is an alkyl hydroxylamine having up to 20 carbons.

3. The combination of claim 1 in which the hydroxylamine is a phenyl or naphthyl hydroxylamine.

4. The combination of claim 1 in which the hydroxylamine contains a carboxy or sulfo group.

5. The combination of claim 1 in which the hydroxylamine contains an alkyl group having from 7 to 20 carbons.

6. The combination of claim 1 in which the hydroxylamine contains a carboxy or sulfo group and in addition an alkyl group having from 7 to 20' carbons.

7. The combination of claim 1, wherein the hydroxylamine is a phenylhydroxylamine, the phenyl ring of which carries an alkyl group having between 7 and 20 carbon atoms, and a water-solubilizing group.

8. The combination of claim 1 in which the hydroxylamine has the formula R--NHOH wherein R represents alkyl having up to 20 carbon atoms, phenyl-substituted alkyl having up to 20 carbon atoms in the alkyl, carboxy substituted alkyl having up to 20 carbon atoms in the alkyl, sulfo substituted alkyl having up to 20 carbon atoms in the alkyl, naphthyl, phenyl, or substitution products of naphthyl or phenyl wherein the substituents are halogen, alkoxy Ehaving up to 18 carbon atoms, hydroxy, carboxy, esterified carboxy having up to 21 carbon atoms, sulfo, amino, acylamino having up to 20 carbon atoms, phenylsulfoamino, alkylamino having up to 20 carbon atoms, sulfamido, acylsulfamide having up to 20 carbon atoms, phenylsulfamido, alkylsulfamido having up to 20 carbon atoms or alkyl having up to 20 carbon atoms.

9. The combination of claim 7 wherein the alkyl group is linlred to the phenyl ring via a phenyl sulfonamide grouping.

1 0. The combination of claim 1 wherein the hydroxylamine 1s o NHOH HOaS g N 11. The combination of claim 1 wherein the hydroxylamine is 12. The combination of claim 1 wherein the hydroxylamine is NH-CiaHgy 13. The combination of claim 1 wherein the hydroxylamine is HOOCCH2(|3HNH0H 14. The combination of claim 1 wherein the hydroxylamine is HOOC-CHr-(fJH-NHOH Cowden et a1. 9628 Trivelli et a1. 9695 Cowden et a1. 9695 Green et a1. 9695 NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner References Cited UNITED STATES PATENTS 5/1947 Trivelli et a1. 9666 US. Cl. X.R. 

